纯CSS实现linear-gradient的渐变动画效果

话不多说，先上效果图

受制于网站的容量，最多只能上传4MB的动图，所以我调快了动画的速度，缩短了动图的时间，实际上动画是很缓和的。

说到动画，众所周知，渐变是不能够使用通过keyframes实现动画过渡效果的，只会突然的改变颜色。

例如，如果关键帧代码如下

@keyframes test {
  0%{
    background: linear-gradient(60deg, rgba(84,58,183,1) 0%, rgba(0,172,193,1) 100%);
  }
  100%{
    background: linear-gradient(60deg, rgb(173, 162, 218) 0%, rgb(201, 14, 189) 100%);
  }
}

可以看到背景色并不会平滑的过渡，只会非常僵硬突然的颜色变化，显然不是我们想要的效果。

换个想法，没必要局限于在keyframes中使用linear-gradient来实现渐变动画效果，linear-gradient不能够平滑过渡，但是position可以呀，所以我们先实现这样的效果

html代码如下

<div class="header">

  <div class="inner-header flex">
    <svg version="1.1" class="logo" baseProfile="tiny" id="Layer_1" xmlns="http://www.w3.org/2000/svg"
      xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" viewBox="0 0 500 500" xml:space="preserve">
      <path fill="#FFFFFF" stroke="#000000" stroke-width="10" stroke-miterlimit="10" d="M57,283" />
      <g>
        <path fill="#fff"
          d="M250.4,0.8C112.7,0.8,1,112.4,1,250.2c0,137.7,111.7,249.4,249.4,249.4c137.7,0,249.4-111.7,249.4-249.4
  C499.8,112.4,388.1,0.8,250.4,0.8z M383.8,326.3c-62,0-101.4-14.1-117.6-46.3c-17.1-34.1-2.3-75.4,13.2-104.1
  c-22.4,3-38.4,9.2-47.8,18.3c-11.2,10.9-13.6,26.7-16.3,45c-3.1,20.8-6.6,44.4-25.3,62.4c-19.8,19.1-51.6,26.9-100.2,24.6l1.8-39.7        c35.9,1.6,59.7-2.9,70.8-13.6c8.9-8.6,11.1-22.9,13.5-39.6c6.3-42,14.8-99.4,141.4-99.4h41L333,166c-12.6,16-45.4,68.2-31.2,96.2    c9.2,18.3,41.5,25.6,91.2,24.2l1.1,39.8C390.5,326.2,387.1,326.3,383.8,326.3z" />
      </g>
    </svg>
  </div>
  <div>
    <svg class="waves" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"
      viewBox="0 24 150 28" preserveAspectRatio="none" shape-rendering="auto">
      <defs>
        <path id="gentle-wave" d="M-160 44c30 0 58-18 88-18s 58 18 88 18 58-18 88-18 58 18 88 18 v44h-352z" />
      </defs>
      <g class="parallax">
        <use xlink:href="#gentle-wave" x="48" y="0" fill="rgba(255,255,255,0.7" />
        <use xlink:href="#gentle-wave" x="48" y="3" fill="rgba(255,255,255,0.5)" />
        <use xlink:href="#gentle-wave" x="48" y="5" fill="rgba(255,255,255,0.3)" />
        <use xlink:href="#gentle-wave" x="48" y="7" fill="#fff" />
      </g>
    </svg>
  </div>
</div>

css代码如下

body {
  margin:0;
}

h1 {
  font-family: 'Lato', sans-serif;
  font-weight:300;
  letter-spacing: 2px;
  font-size:48px;
  user-select: none;
}
p {
  font-family: 'Lato', sans-serif;
  letter-spacing: 1px;
  font-size:14px;
  color: #333333;
}

.header {
position: relative;
    text-align: center;
    background: linear-gradient(
45deg, rgb(84 58 181), rgb(84 58 181 / 70%), rgb(0 172 193 / 70%), rgb(87 228 246),rgb(255 255 255));
    color: white;
    box-shadow: 1px 1px 6px #00000087;
}
.logo {
  width:50px;
  fill:white;
  padding-right:15px;
  display:inline-block;
  vertical-align: middle;
}

.inner-header {
  height:65vh;
  width:100%;
  margin: 0;
  padding: 0;
}

.flex { /*Flexbox for containers*/
  display: flex;
  justify-content: center;
  align-items: center;
  text-align: center;
}

.waves {
  position:relative;
  width: 100%;
  height:15vh;
  margin-bottom:-7px; /*Fix for safari gap*/
  min-height:100px;
  max-height:150px;
}

.content {
  position:relative;
  height:20vh;
  text-align:center;
  background-color: white;
}

/* Animation */

.parallax > use {
  animation: move-forever 25s cubic-bezier(.55,.5,.45,.5)     infinite;
}
.parallax > use:nth-child(1) {
  animation-delay: -2s;
  animation-duration: 7s;
}
.parallax > use:nth-child(2) {
  animation-delay: -3s;
  animation-duration: 10s;
}
.parallax > use:nth-child(3) {
  animation-delay: -4s;
  animation-duration: 13s;
}
.parallax > use:nth-child(4) {
  animation-delay: -5s;
  animation-duration: 20s;
}
@keyframes move-forever {
  0% {
   transform: translate3d(-90px,0,0);
  }
  100% { 
    transform: translate3d(85px,0,0);
  }
}
/*Shrinking for mobile*/
@media (max-width: 768px) {
  .waves {
    height:40px;
    min-height:40px;
  }
  .content {
    height:30vh;
  }
  h1 {
    font-size:24px;
  }
}

再然后，我们把背景放大，也就是在.header中加上这一行代码background-size: 400%
然后写一个背景移动的关键帧动画

@keyframes gradient {
    0% {
        background-position: 0% 50%;
    }
    50% {
        background-position: 100% 50%;
    }
    100% {
        background-position: 0% 50%;
    }
}

应用到.head中

.header {
position: relative;
    text-align: center;
    background: linear-gradient(
45deg, rgb(84 58 181), rgb(84 58 181 / 70%), rgb(0 172 193 / 70%), rgb(87 228 246),rgb(255 255 255));
    background-size: 400%;
    color: white;
    box-shadow: 1px 1px 6px #00000087;
    animation: gradient 5s linear infinite;
}

调整动画速度只要修改animation中的5s就行了，随便改成什么数字就行。

底部的渐变波纹动画来自于该网站
https://codepen.io/goodkatz/p...